1. Field of the Invention
The present invention relates to use of an optical fiber. More particularly, the present invention relates to an apparatus and method for measuring a concentration of each component of a target material using light having wavelengths discretely converted through an optical fiber.
2. Description of the Related Art
As a person""s living environment and conditions continue to improve, one""s interest in personal health increases. As a result, a variety of household medical devices, which allow the condition of a person""s health to be easily checked at any time, have been developed.
In a human body, body fluids are circulated and adjusted so that the amount of each body fluid may be maintained within a particular normal range. Body fluids, for example, include blood, urine, interstitial fluid, sweat, and saliva. Particularly, the concentration of each component, such as sugar or protein, in body fluids such as blood or urine is very useful in determining a person""s health condition. In addition, to determine a person""s health condition, concentrations of glucose, hemoglobin, bilirubin, cholesterol, albumin, creatine, protein, and urea may be measured.
When a living body becomes sick, a change occurs in the composition and/or the amount of one or more components of body fluids. Accordingly, one""s health condition may be checked by measuring a concentration of one or more components of a body fluid. For example, the concentration of blood glucose in a normal person is about 80 mg/dl before a meal and about 120 mg/dl after a meal. In order to maintain such a concentration of blood glucose in a living body, the pancreas secretes a proper amount of insulin before or after a meal so that the insulin may be absorbed into the liver and the cells of skeletal muscle. When the pancreas does not secrete enough insulin to maintain a normal blood glucose level due to illness or other reasons, however, a blood glucose level excessively increases. An excessive increase may cause a cardiac disorder, liver trouble, arteriosclerosis, hypertension, cataract, retinal hemorrhage, injury to nerves, hearing loss, amblyopia, or even death in a worst case. Accordingly, it is very important to be able to evaluate any change in a component of body fluids in an organism without being limited by time or location.
Two representative methods of measuring a concentration of a component of body fluids are an invasive method of directly taking a sample of a target material to measure the concentration of a component and a non-invasive method for measuring the concentration without taking a sample of a target material. According to a usual invasive method for measuring the concentration of a component of a body fluid, a blood sample is taken, a reaction between the blood sample and a diagnosis reagent is analyzed using clinical analysis apparatus, and the concentration of the component is measured based on the result of the analysis. In such an invasive method, however, the taking of blood samples may be painful and may expose a diabetic patient to a risk of infection. Moreover, it is difficult to monitor the patient continuously. Thus, in the case of an emergency, a patient may not be timely and properly treated. In addition, the invasive method requires the use of many expendable supplies, such as strips or reagents, which places a financial burden on a patient and causes environmental pollution. Accordingly, there is motivation to develop technology for measuring the concentration of blood glucose non-invasively for the purpose of controlling blood glucose in diabetics or checking a person""s health condition.
In most spectroscopic methods used for measuring a concentration of a component of a body fluid in an organism, light having an optical wavelength of a visible ray or a near infrared ray (NIR) is radiated at a portion of tissue in the organism, and light reflected from or transmitted through the organism is detected to estimate the concentration of a component of the body fluid. Here, light having a wavelength most readily sensitive to a particular component to be measured and reference light having a wavelength within a band allowing influence by an interfering material to be effectively countervailed are necessary.
A conventional apparatus for measuring a concentration of a component measures a spectrum using a continuous wave (CW) light source and calculates the concentration from the measured spectrum or calculates the concentration using a plurality of light emitting diodes (LED) or laser diodes (LD) as a light source. However, since the concentration of a component to be measured is very low and the effect of scattering of light is greater than the influence of absorption of light in organic tissue and blood, a detected signal may be weak. Accordingly, a method for increasing the magnitude of a signal is required, but average energy applied to a body should be outside of a range in which the tissue of the body may be damaged. Particularly, in an NIR range of 700-2500 nm, a glucose absorption band is widely spread, and a glucose absorption peak is relatively small against a wide background spectrum with respect to water, so a signal to noise ratio is small. Accordingly, it is difficult to measure an accurate concentration.
It is a first feature of an embodiment of the present invention to provide an apparatus capable of easily generating light having a plurality of discrete wavelengths and radiating the generated light at a target material to measure a concentration of each component of the target material.
It is a second feature of an embodiment of the present invention to provide a method performed using the above apparatus to measure a concentration of each component of the target material.
To provide the first feature of an embodiment of the present invention, there is provided an apparatus for measuring a concentration of a component of a target material. The apparatus includes a pumping light source for emitting light having a single wavelength having peak power of at least a predetermined value; a first wavelength conversion unit for converting light incident from the pumping light source into light having at least one discrete wavelength and outputting the converted light; a first beam splitting unit for splitting the converted light incident from the first wavelength conversion unit into light beams and directing a first light beam at the target material; a reference light generator for converting a second light beam generated by the splitting performed in the first beam splitting unit to be parallel, dividing the parallel light beam by wavelengths, and outputting the result of the division as reference light; a first collimating unit for converting light transmitted through the target material to be parallel and outputting the parallel light; a light intensity measuring unit for measuring the intensity of light incident from the first collimating unit and the intensity of the reference light, by wavelengths, using the reference light; and a concentration measuring unit for measuring the concentration of the component based on the intensities measured by the light intensity measuring unit by wavelengths.
In another embodiment of the present invention, there is provided an apparatus for measuring a concentration of a component of a target material. The apparatus includes a pumping light source for emitting light having a single wavelength having peak power of at least a predetermined value; a second through 2V-th beam splitting units, wherein V is at least 2; a second through (V+1)-th wavelength conversion units; a total reflector; a reference light generator for converting a light beam generated by a splitting performed in each of the (V+1)-th through the 2V-th beam splitting units to be parallel, dividing the parallel light by wavelengths, and outputting the result of the division as reference light; a first collimating unit for converting light transmitted through the target material to be parallel and outputting the parallel light; a light intensity measuring unit for measuring the intensity of light incident from the first collimating unit and the intensity of the reference light, by wavelengths, using the reference light; and a concentration measuring unit for measuring the concentration of the component based on the intensities measured by the light intensity measuring unit by wavelengths, wherein the second beam splitting unit splits light incident from the pumping light source into light beams and outputs one of the light beams to the second wavelength conversion unit, the v-th (3xe2x89xa6vxe2x89xa6V) beam splitting unit receives and splits one of light beams generated by the splitting performed in the (vxe2x88x921)-th beam splitting unit into light beams and outputs one of the light beams to a v-th wavelength conversion unit, the total reflector totally reflects one of the light beams generated by the splitting performed in the V-th beam splitting unit to the (V+1)-th wavelength conversion unit, the w-th (2xe2x89xa6wxe2x89xa6V+1) wavelength conversion unit converts incident light into light having at least one discrete wavelength and outputs the converted light, and the (V+wxe2x88x921)-th beam splitting unit splits light incident from the w-th wavelength conversion unit into light beams and outputs one of the light beams at the target material.
To provide the second feature of an embodiment of the present invention, there is provided a method for measuring a concentration of a component of a target material. The method includes emitting light having a single wavelength having peak power of at least a predetermined value; converting the emitted light into light having at least one discrete wavelength; splitting the converted light into light beams, directing a first light beam at the target material, converting a second light beam to be parallel, and dividing the parallel converted second light beam by wavelengths to generate reference light; converting light transmitted through the target material to be parallel; measuring the intensity of the parallel converted light and the intensity of the reference light, by wavelengths; and measuring the concentration of the component based on the intensities measured by wavelengths.